The present invention relates to a method for producing a record carrier, and more particularly for producing a record carrier which can be used for the production of phonograph records.
German Pat. No. 2,811,888 and corresponding U.S. Pat. No. 4,248,438 to Knothe et al. disclose a method for producing a metal matrix provided with a groove modulation. In the process disclosed in these patents, a thin layer of copper is initially electrochemically deposited from a copper bath onto a substrate. The groove modulation is then cut into the copper layer electromechanically by means of a cutting stylus which is guided over the metal matrix. The electrochemical bath contains brightener additives which impart a Vickers hardness between 110 and 300 to the copper layer. When cutting the groove modulation, the cutting stylus is guided over the metal matrix at an angle between 10.degree. and 20.degree..
In this prior art process, a cuttable layer of copper is precipitated which is suitable for the production of video recordings, but which does not satisfy the demands for the production of phonograph records made with an analogous cut with a much greater modulation depth. The use of the known teachings disclosed in the above patents leads to the precipitation of a copper layer which is not suited for cutting sound recordings. Due to the much greater cutting depth for analog sound recordings than for digital or frequency modulated video recordings, the copper presents a much greater resistance to the cutting stylus.
In the conventional technology for producing phonograph records, a cuttable layer of nitrocellulose is applied onto a substrate of, e.g., aluminum and the modulation is cut into this nitrocellulose layer. Compared to a cuttable copper layer, a lacquer layer is much softer and presents a much lower resistance to the cutting stylus. The quality of a lacquer recording is limited, however, because it experiences system-caused errors, such as leading and trailing echoes.